1. Field of the Invention
The invention relates to a force/tactile feedback device for feeding back a force sense or a tactile sense to an operator in a simulation space in which physical environment is exquisitely calculated, a simulation space in which physical environment is artificially or simply calculated or in an actual physical space in a master/slave relationship, particularly, relates to a force/tactile feedback device feeding back a gripping sense to fingertips of the operator.
More particularly, the invention relates to a force/tactile feedback device feeding back the force sense to fingertips of the operator as well as feeding back a shape by driving of plural finders, particularly, relates to a force/tactile feedback device not only feeding back the force sense or the tactile sense with respect to a fixed contact point but also feeding back a position of the contact point on which a contact state is reflected.
2. Description of the Related Art
In a technical field of virtual reality or telereality, a force sense display, namely, “haptic device” for feeding back a force sense or a tactile sense to the operator in addition to visual information and hearing information is indispensable.
Along with the improvement of computer speed and the progress of a simulation technology, virtual environment in which plural objects exist and physical interaction such as crashes or contacts occurs between them can be simulated in actual time. When a crash between objects or a contact force at that time can be calculated exquisitely as well as in actual time in consideration of dynamics, senses when the user touches or grips objects in the virtual environment through the haptic device can be fed back to the user with reality by actually generating the calculated force by an actuator such as a motor.
Applications of the haptic device are wide, which are used for feeding back a force sense or a tactile sense to the operator in the simulation space in which physical environment is exquisitely calculated, the simulation space in which physical environment is artificially or simply calculated or in the actual physical space in the master/slave relationship. Specifically, in learning of special skills such as medical care or the like, virtual environment such as microcosms or oceans, and remote operations in special or dangerous environment such as a nuclear reactor, a three-dimensional force or tactile sense with respect to objects in environment which are difficult to be actually touched can be fed back. According to scale or accuracy of the virtual space which can be processed in actual time, increase of demand of the force display in the future is expected.
For example, a pen-type haptic device using serial links as shown in FIG. 18 is common. The user grips a tip portion of the pen shape, in which 3-axial force to 6-axial force moment is fed back (for example, refer to JP-T-2007-510232 (Patent Document 1), http://www.sensable.com/haptic-phantom-desktop.htm (as of H19, October 9) (Non-Patent Document 1)). The haptic device in the drawing includes an operation system such that the operator just has a pen (or a probe), having a structure in which a 3 degrees of freedom arm and 3 degree of freedom gimbal are connected so that an arbitrary space position and the moment are fed back with respect to a specific portion such as a pen tip. According to such kind of device, a translation force and the moment can be generated at an arbitrary position in principle, however, a sense to be obtained is as if picking with the pen because the operation system by probing is a keynote, which does not give a sense of gripping the object.
A haptic device feeding back 3-axial force to 6-axial force moment by using a parallel link structure is proposed as a structure for solving lack of stiffness of the serial link as shown in FIG. 19 (for example, refer to Japanese Patent No. 3329443 (Patent Document 2), http://forcedimension.com/fd/avs/home/products/ (as of H19, October 9) (Non-Patent Document 2), http://www.quanser.com/industrial/html/products.fs—5dof.asp (as of H19, October 9) (Non-Patent Document 3)).
In any of the above haptic devices using the link mechanisms, a force sense is fed back with respect to one point of a gripping position, in other words, the force sense is not fed back to respective fingers of an operator independently. Accordingly, there is a problem that it is difficult to feed back the sense of gripping a virtual object by fingers.
As functions of the haptic device, a force sense feeding back force itself, a tactile sense feeding back a contact state can be cited. It goes without saying that a moving tactile sense usually performed by a human being is included. In order to realize these functions, not only force control ability which is necessary for haptics but also position feeding back ability reflecting a shape of a physical object, further, excellent response, namely, speed and acceleration control ability are necessary for realizing the moving tactile sense. There is also a method that the force sense is sharpened by the pen (probe) type and the like. However, in order to know the shape of the physical object, it is natural that there are plural contact points as in the case of grasping the object by plural fingers.
For example, a multi-finger type haptic device has an advantage that the shape of a target object can be fed back by driving of plural fingers. A slave hand such as a robot hand is applied to a master hand which performs remote operation, thereby having a function that the motion of the master hand (operation means) is transmitted to the slave hand (work means) as well as a force sense of the slave hand is fed back to the master hand. That is, an operator of the master side can obtain the sense as if performing operation directly to an operation target. According to the multi-finger type haptic device, it is possible to feed back a force sense to operator's fingers as well as to feed back the shape by driving of plural fingers.
In order to feed back the force to plural fingers, as shown in FIG. 20, a haptic device in which fingers and remote motors are connected by wire and the force is applied to respective fingers through the wire is proposed (for example, refer to http://sklab-www.pi.titech.ac.jp/frame_index-j.html (as of H19, October 9) (Non-Patent Document 4)). However, it is necessary to control so that the wire is not slackened, which may complicate the control. In addition, the interference between wires is liable to occur, particularly, the range in which the device can move concerning rotation is not so wide.
A haptic device in which a hand-type force feedback mechanism is added to an opposed manipulator as shown in FIG. 21 is also proposed (for example, refer to “opposed-multi fingers haptic interface” attributed to KAWASAKI Haruhisa, HORI Takumi and MOURI Tetsuya (Journal of the Robotics Society of Japan Vol. 23, No. 4, pp 449-456, 2005) (Non-Patent Document 5)). As a method similar to this, a method of adding a hand-type force feedback mechanism to tips of an exoskeleton is also proposed (for example, refer to http://www.immersion.com/3d/products/cyber_grasp.php (as of H19, October 9) (Non-Patent document 6)).
A method in which a fingerstall is provided at a tip of the serial link to feed back 3-axial force to a finger is also proposed.
For example, there is also proposed a force sense feedback device in which a 6-axial force sensor including a fingerstall into which a finger of a human being is inserted, a finger cover touching an object and an elastic structure which is between the fingerstall and the finger cover, to which a strain gauge is adhered, is connected to a base through a small manipulator (for example, refer to JP-A-2002-182817 (Patent Document 3)). According to the force sense feedback device, a force sense is fed back to fingertips of a human being as well as force sense data when a human being actually touches an object can be recorded/played back.
Additionally, there is proposed a tactile sense/force sense feedback system including a pair of real gloves which is worn on hands (fingers) of a user, giving a tactile sense (a touching sense, for example, distribution of touching intensity such as quality, shape or strength) or a force sense (sense of force added at the time of touching) to the hands or respective fingers on which the gloves are worn (refer to JP-A-2003-323247 (Patent Document 4)), in which tactile sense generation units are provided respectively at positions covering fingertip portions from first joints (a joint between a distal phalanx and a middle phalanx) of respective fingers of the user.
Also, there is proposed a force display hand including an elastic expansion/contraction structure in which plural skeleton materials are connected by connecting portions so as to move as well as fixed among plural skeleton materials over the connecting portions, further including fingerstalls or a glove connected to the skeleton materials as well as engaged to at least fingers, a palm or a part of a hand including a back of the hand, which gives an artificial force to the part of the hand by expanding or contracting the elastic expansion/contraction structure (for example, refer to JP-A-2004-29999 (Patent Document 5)).
However, in any of above related arts concerning the multi-finger type haptic devices, only translation force is fed back to fingertips, and it is difficult to feed back contact points of respective fingertips, namely, points of action. Therefore, it is difficult to feed back the gripping sense to plural fingertips in a good state.
It is important to directly touch an object by fingers of a human being for obtaining a contact sense clearly. In this light, a force/tactile feedback device capable of acquiring contact point information by an operator by allowing fingertips to touch spherical protrusions and by changing positions thereof is proposed (for example, refer to http://telerobotics.stanford.edu/publications/Provancher03-ISRR-Perception.pdf (as of H19, October 9) (Non-Patent Document 7), http://bdml.stanford.edu/twiki/bin/view/Haptics/ContactLocationDisplay (as of H19, October 9) (Non-Patent Document 8)). The device is configured to clearly feed back positions of contact points by rolling rollers which touch the fingertips of the operator directly, whereby the operator obtains contact sense more sensitively. However, the rollers for feeding back contact points touch the fingers at any time, therefore, unnecessary contact information is transmitted to the operator when the rollers move even when a force to be fed back is not generated. In addition, the operator senses the contact more sensitively because of the direct contact, therefore, the operator feels odd more sensitively.